Vessels in sight of one another

Saying that another vessel was detected does not say how it was detected. Rule 3(k) considers vessels in sight when one can be observed visually from the other. Rule 11 applies Rules 11–18 to that condition. An AIS position or radar echo alone does not constitute visual contact. This small distinction changes which encounter rules are relevant and should be resolved before using a crossing, sailing or overtaking sketch. The condition belongs to the legal framework, rather than being an optional label added after a decision.

Detection identifies presence through a particular means. Observation adds what was actually seen or measured. Interpretation relates that evidence to a classification. A display can supply range, velocity or a declared identity without showing the vessel visually. A visible silhouette can establish presence without proving its activity. Rule 7 prohibits assumptions from scanty information, making visual contact and sufficient information related but distinct questions. A useful account describes the means and evidence rather than promoting every electronic label into an established legal status.